Make classes and structures in Source/core/animation fast-allocated.

Source/core/animation/DocumentAnimation.h

Index: Source/core/animation/DocumentAnimation.h
diff --git a/Source/core/animation/DocumentAnimation.h b/Source/core/animation/DocumentAnimation.h
index 69002d2575f6277b57c666693bb7301cb8f5ac14..7d6ab3f21cad4edebc1c0c8f92a9235486fd7659 100644
--- a/Source/core/animation/DocumentAnimation.h
+++ b/Source/core/animation/DocumentAnimation.h
@@ -6,10 +6,12 @@
 #define DocumentAnimation_h
 
 #include "core/dom/Document.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
 class DocumentAnimation {
+    STATIC_ONLY(DocumentAnimation);
 public:
     static AnimationTimeline* timeline(Document& document) { return &document.timeline(); }
 };